1. Field of the Invention
This invention relates generally to stepper motors, and more particularly to a stepper motor controller implemented in a minimal amount of silicon space.
2. Related Art
Printers, such as inkjet printers, use a stepper motor to feed paper. A controller for the stepper motor resides in the printer, such as in the form of an application specific integrated circuit (ASIC). A table of information used by the controller to control the movements of the stepper motor is "hard-coded" in the ASIC. The phase table contains an entry for each operating state of the stepper motor and corresponding output signals (phase signals which determine current direction and current level signals) for a stepper motor driver circuit. For certain motor drivers, the phase signals in some states change depend on the direction that the motor is running.
The phase table values change from printer to printer to accommodate different printer characteristics. Examples of characteristics that differ among printers are driver circuits, motor torque, acoustics and power consumption. It is desirable to have a phase table that is programmable by the printer software so that the values of the phase table can be determined later in the product development cycle. A software-programmable phase table also allows for the use of different phase tables for different operations or modes in the printer, thereby optimizing the stepper motor characteristics for a particular move.